Experimentelle Untersuchung einer kompressiblen Stoß-Scherschichtwechselwirkung in Überschallströmungen

摘要

The technical focus of this doctoral thesis:"Experimental Research of a Compressible Shock-Shear Layer Interaction in Supersonic Flows", is a Scramjet engine. This is a Ramjet engine in which fuel is injected, mixed and burned in a supersonic air flow. Supersonic combustion in a Ramjet is necessary for a fight velocity higher than Mach number M = 5. This thesis deals with supersonic mixing. Supersonic compressible shear layers and the influence of shocks on shear layers were experimentally investigated. The Scramjet combustion chamber model has a central fuel injection element, which injects hydrogen gas with a Mach number M = 2 parallel to the supersonic air flow. In this investigation the air flow was accelerated to the Mach number M = 2. The compressible supersonic shear layers were investigated using the following measurement methods: Schlieren optics, pitot tubes, Laser-Two-Focus system (L2F), Laser-Induced-Fluorescence (LIF) and Rayleigh scattering. The convective Mach number Mc, a characteristic number for compressible shear layers in supersonic flows, was varied in the range from Mc = 0,7 to 1,34. The compressible growth rate was normalized with the incompressible growth rate of the shear layer. The experiment shows, that the normalized growth rate of the compressible shear layer strongly decreases with increasing convective Mach number and that the normalized growth rate moves toward 0,3. Similar to the incompressible shear layers, the compressible shear layer also shows big vortex structures. These structures were compressed and stretched vertically with increasing convective Mach numbers. Defined shocks with different strengths were induced on the compressible shear layer with a wedge on the upper model combustion chamber, and the shock-shear layer interaction was investigated. Shocks locally improve the mixing near the interaction zone in the compressible shear layer. With a shock-shear layer interaction the normalized growth rate increased up to +50%. With increasing convective Mach number Mc the improvement of mixing decreases down to +20%.